Rapid Fabrication Of Through-hole PAA Templates And Construction Of Nano Capacitors

Highly ordered porous anodic alumina?PAA?templates have been widely used to prepare various kinds of functional nanomaterials,but the rapid fabrication of through-hole PAA templates is still a challenge.In order to construct a dielectric capacitor based on aluminum nanowire arrays,a rapid fabrication method of through-hole PAA templates with different diameters was developed.Highly ordered and large-scale aluminum nanowire arrays were successfully fabricated using the through-hole templates by the optimization of the melting injection process under high temperature and pressure.The dielectric oxide layer was achieved by anodization of aluminum nanowire arrays to assemble nanocapacitors.Firstly,the influence of applied voltages and H₂C₂O₄ concentrations on the ordering degree of PAA were explored.The results showed that the increase in H₂C₂O₄ concentrations and applied voltages can effectively improve the ordering degree of PAA films.The PAA obtained at 62 V in 0.75 mol L-1 H₂C₂O₄ electrolyte exhibited the best ordering degree of 75.6%with the growth rate of 134.54 ìm h-1.The barrier layers for PAA templates formed at 62 V by single-side oxidation and at 48 V by double-side oxidation were selectively etched for 150 min and 40 min,respectively,their barrier layers could be completely removed and the through-hole PAA templates were acquired.Secondly,in H₃PO₄ ethanolic solution and H₂C₂O₄ electrolyte of low concentrations,PAA films with large interpore distances were obtained under high voltages at room temperature.However,the issues such as slow growth rate and irregular PAA channels still remain.In some monosubstituted phosphate electrolytes,rapid preparation of PAA with large interpore distances can be realized.The applied voltages could range from 200 V to 380 V.The growth rate of PAA in the monosubstituted phosphate electrolytes was about 30-60 times higher than that in conventional phosphoric acid electrolytes.By selective etching of PAA formed at 340 V for 8 h,the through-hole PAA template was obtained.In addition,the dielectric properties of barrier alumina films fabricated on polished aluminum was investigated.The influences of electrolyte compostion,anodizing temperature,and anodizing time on dielectric performances of alumina films were explored.The results showed that the dielectric films fabricated in diammonium citrate and ammonium borate electrolytes demonstrated low leakage currents.The best dielectric performance was observed on the dielectric film formed at 40?.The addition of a small amount of phosphoric acid monobutyl ester into diammonium citrate solution can reduce the contaminant layer of alumina dielectric film at the same applied voltage,thus significantly reducing the leakage current of dielectric film.The leakage current of dielectric film can further decrease with the increase of the additive concentration.Finally,aluminum nanowire arrays with different diameters were fabricated through PAA templates with different diameters under different injection vacuum melting process.The influence of different injection processes on aluminum nanowire arrays was studied.The optimum process condition was that the pressure should be at 65 MPa,and the injection temperature should be lower than the melting point of aluminum?660??.The pressure was applied at 200? by up to 65 MPa,and then the pressure maintained and the temperature was raised gradually to 400 ?.After a period of time,the temperature was raised slowly to 650 ?and the highly ordered aluminum nanowire arrays with large scale were successfully achieved.The dielectric layer was fabricated by anodization of aluminum nanowire arrays to assemble nanocapacitors.At 50 Hz,the capacitance of dielectric layer based on aluminum nanowire arrays was 20.8 times higher than that of the flat dielectric capacitor.